Automatic switching system



1927. June 28 `F.,\\ c rr-1|3oR|=F AUTOMATIC SWITCHING A SYSTEM Filed Janlz. 1923 '7 Sheets-Sheet 1 jh; @Maule June 2s. 1927.

'7 Shasta-Sheet 2 'Filed Jang-S. 1923 F ALDENDORFF AUTOMATIC SWITGHING SYSTEM 7 .o m u m jm M 6 A l, m m wh/M Nw m wm 4 mom @om d@ 7 Qrlll w 1 n 9mm nw Ml i w 2 mq Q n m am s {Tul F Y 3 M m m l m .f N T 2, mQ m m T w. m F m m T w.

'June 28, 1927.

"June 28. 1927.

F.l ALDENDORFF` vAUTor'mTIc SWITCHING SYSTEM Filed Jan.29. 1925 'T ,Sheets-Sheet 4 @imm 25 IIE:

1927. June 28 F. ALDENDORFF AUTOMATIC SWITGHING SYSTEM Filed Jan.g9. 1925 'r sheets-sheet 5 l 1927. June 28 F. ALDENDORFF AUTOMATIC SWITCHING SYSTEM Filed Jan. 29. 192:5

7 Sheets-Sheet 5 7 Sheets-Sheet 'T F. r ALDENDORFF AUTOMATIC SWITCHING SYSTEM Flled Jan 2S,

, Y ggf* l E+ l Patented June 1927.

e i UNITED STATES PATENT OFFICE.Y

FRITZALDENDORFF, F WILMERSDORE, NEA-R BERLIN, GERMANY, AssIGNoR 0E ONE- FOURTH To PAUL KoLIsoH, 0E NEW YORK, N. Y.

AUTOMATIC SWITCI-IING SYSTEM.

Application ined Janiiary 29,1923, serial No This invention relates in general to automatie switches and telephoneswitching systems and more particularly to systems in which novel types of selectors or switches :fre en'iployed whose movable contacts "an be f set onto any contactorset of contacts in a which is a semi-conductor and one of which yparts so as fixed to the brush carriern'hile the other is held stationary, electric vcircuits being arranged to (2o-operate with said conducting to cause them to adhere firmly to each other at the right moments. The semi-conductor is a material of high electric resistance such as the slate `used by lithographers and which is found in large quanti- 'ktics near Solenhofen in Germany. Instead of thek Solenhofen slate, ragate may be employed. f A feature of the invention is a selector' u ith lfiankcontacts, wipers cooperating with the bank contacts and a wiper carrier whose movements are controlled by currents that affect a part moving together with the wiper carrier and another part continually bearing against the first part. Thecurrents controlling the movements of the wiper carrier are preferably sent through the part that moves together with the wiper carrier and the part bearing' against the said firsty part. The wiper carrier is preferably moved` by a continuously acting force and stopped by currents sent through a semi-conductor contacting with a part belonging to, ory moving with.

i the wiper carrier and through the bank contacts and wipers` of the switch. When the switch isused as a finder the controlling or stopping currents are sent through the semiconductor, a wiper and a bank contact of the switch to which a potential is applied by an element belonging to a calling line or trunk. \Vhen the switch is used as a group select-or, the controlling current-s are sent through the semi-conductor, a wiper and group designating bank contacts of the selector, yT he wiper 615,627, and in Germany February 2, 1922.

carrier, aft-er being driven up to the desired bank Contact group, is preferably driven `irther in a continuous movement, until the wipers are stopped on a free trunk by a current sent through the semi-conductor, a wiper of the switch and a bank contact associated with the free trunk. TWhen the switch is yused as a connector or final selectorthe controlling current is sent through the semiconductor, a wiper and group designating contacts, and then through line designating ccntacts instead of the group designating contacts. y

1n order to ensure that an intimate contact `is maintained between all parts of the semi-conductor 'and the surface of the part thatk moves relatively thereto, a yielding connection is preferably provided between the wiper carrier and the part bearing against the semi-conductor. y

The wiper carrier or propelled member of the switch is preferably driven by a. tensioned spring. lVhen the switch is used as a numerical selector, the propelling yforce is controlled by applying potential to one bank contact ofthe switch after another.

In the group selector stopping bank contacts are provided at the end of each group of bank contact sets for stopping a hunting wiper. A similar arrangement be used in final selectors or connectors arranged for l). B. X. hunting.

The semi-conductor in the switch may be in the form of a cylinder surrounding the wiper carrying shaft, or itmay be made in the form of a flat disk against which a` metal disk rotated with the' wiper-carrying-shaft bears.

A close-fitting split spring ring may be inserted between the semi-conductor cylinder and its bearing, and the ring may be arranged to drive a stopping pawl into the teeth of a disk fined to the wiper carrier.

Another feature of the invention consists of means for treating or cleaning the surface of the semi-conductor which contacts with the metal part or disk attach-ed to the wiper carrier or shaft of the switch or selector.

Other features of the invention will appear hereinafter in the drawing, description and claims.

The invention is showiiinthe drawing in which Figs'. 1 and Q'are an elevation partly in section and a plan view of the new selector in which a 'semi-conductor is used for the CII purpose ot enabling the movable contacts of the switch to be moved round at a great speed and yet to be stopped instantaneousl)v on reaching any desired set ot' contacts4 in the Contact bank of the switch.

Figs. 3 and et show circuits that may be used in connection with the novel switch.

Figs. 5 and 6 are a plan View and vertical section respectively ot a modified bearing and arresting,` device for the switch shown in Figs. 1 and 2.

Fie. 7 is an elevation and Fig. 8 a plan view of another inodilied switch in which the semi-conductor has the torni ot a flat dish.

Fig'. 9 is a diagrammatical vertical section of Fig. l in which the mechanical connection between the wiper carrier or shaft and the instal disk that contacts with the semiconductor disk is more clearly shown.

Figs. 10. 11 and 12 show the circuits ot a line inder, group selector and connector respectively ot the type shown in Figs. T 8 and 9.

F 13 illustrates a modification of the starting circuits for line inders which opcrater in general in the saine manner as the starting circuits shown in 3.

Fig. 1-1- is an elevation ot a device lor treating or cleaninY the surface ot the semiconductor which contacts with the metal oisl connects-d to the shaft of the wiper.

Fie'. 15 shows a detail ot F 1+i and 1F is a cross section through the brush oi the cleaning device ol 1l.

Fig'. 1'? is a sectional view ot a moditied flexible mechanical connection between 'the contacting` metal dish and the shaft otf a switch et the tjvpe shown in Figs. N

ln Fig. 1, 1. :2, l and si are i .ur brushes which project out in two oppor" directions from the rotar); member ot the si. itch. rotary member consi t ot.' a toothed wheel 5 to which a pin or shaft 6 is ivefl. a top rotary i'iortion consistiug;` ot a sleeve T with a. flange o made i' semi-coiuluctor. a metallic core i) with a flanged bottom portion 10, an ot layers ol packing material ll. l2. 12% an "4rbetween which the brushes l,v il and el;

, einbeclnsd. 'lhe brushes l. :2rv l and 4t insulated 'troni the bod)Y oit the switch l from each otherl b v suitable la'vers ot nirlation. rl'he toothed wheel has holes 5 and 16 through which screws 17 and 18 re inserted which serve to hold all the parts (l, 7, S, Sl. lll. il, 12, 13, 1i ot the rotor together. The sleeve 7 which ot the switch is made of a semi-insulatm' is jourualled in a bea 'ing lil that is designeel so as to exert. a certain pressure against the sleeve T so as to continually establish an. intimate mechanical contact. The lower shaft tl is journalled in a sleeve 2O which is combined with a musing 21 provided at the rear with a i'lange or lug 22 by which the housin"` 2l is screwed tast to a rack or traine. A spiral spring or clock springl 2S is disposed inthe housing 21, its one end being attached to the lower shaft 6 and its outer end being lixed to the housing'. rFhis spring is tensioned and tends to rotate the rotor with the brushes l., 2, 3, tat a relatively high speed. The rotor is. however` held in its normal position by a detent 24, Fig. 2, adapted to swine' around the pivot The detent hai an arrowshaped end 2o with two oblique surtaces adapted to be engaged by the roll Q7 ot a rocher arm 29 whose upper end is acted upon by a spring 30. ln the p sition shown in Fig'. 2 the roll Il' engages with the upper oblique surface ot the arrow-sluzped end ot the detent 24C thus tendingl to swing the detent 2d round clockwise so that its lett end 3l engages with a pin 32. The lett end of the detent 2i has a cam surilace $35 and a detaining tooth 30 which holds the toothed wheel 5 against rotation in the direction ot the arrow 2T. When a current impulse is sent through the magnet 38 'this magnet attracts its armature 39 whereupon the propelling' pawl '-10 engages with a tooth ot' the wheel 5 and rotates it in the opposite direction to that ot the arrow 3T. The pin l2 lined to the wheel 5 then rides up on the cani surface and throws the detent 2l round in a eounter-eloehwise direction and causes the detainiuiz tooth 35 to release 'the det innig' pin S3 so that the wheel o is rotated by the spring 23, litigi'. l. in the direction of the arrow 3T.

ill'hen the detent is turned counterclocliwise its awow-shaped end 2o if., ,ri upward fio that the roll engages w.I the lower ohlioue surtace of the head il" rl`he detent 2l provided with a restoring arm l1 which is brought into the path ot a restoring' pin -l-Q when the de'ent is swungi' round counter-chufhwise by the pin i312 as dcscril'ied. ll'hen the wheel o ha.`l rotated through a certain angle so that the holding; piu 3.53 has travelled parat the detaiuinc tooth 3o the resten-'ingl pinv '32 str' s against the inner end ot the restoring arni -l-l and restores the detent 2l; into i 'f normal position in which the roll 2? eno` .g s with the 'upper oblique suriiace ol" the arrmv-sliapel head 26 of the dele it :Z-las shown in Figi ll'vhen the wheel is restored to its normal position by 'further impulses sent through the magnet 3S the holding' piu I-l'l slips over the top ot' the detaiuingr tooth 36 and rotates the detent through a small angle, without causing?, the roll il? to leave the upper oblique surface. oi" the arrow-shaped cuchillo ot the detent 2l. rl`he moment the holding' pin 33 slips down at the right hand side. of the holding tooth 36, or more correctly speaking', the moment the holdingtooth 315 slips up at the lett hand side ot the, holding pin 33 the left hand end of the detent lili) 24 enters into engagement with ythe release pin and the partsk will then have regained the position shown in Fig. 2.

The' shaft 9 of the switchmay he providedwith a recess with which the spring 43 of an oiinorn'ial switch engages as long as the switch is in its normal position.y The moment the switch leaves its normal position the spring 43 leaves the spring* 44'y and is caused to make Contact with the spring 45.

The Wipers 1, 2, 3 and 4 travel over bank `contacts Which are not shown in Figs. 1 and 2. The circuits of the switch are arranged so that the moment a wiper, as 1, strikes the contact of any desired contact set in the bank 1 current is caused to'flow through the fixed metallic journal 19 the rotary sleeve 7 made of a semi-conductor and through the metallic core 9. The adhesive force which is then instantaneously setl up between the fixed 4journal 19 and the rotary sleeve 7 causes the latter to stick in the bearing and the brushes 1, 2, 3 an'd 4 are then 'stopped on the particular' set of bank'contacts in ques tion.

The switch may be usedas aline finder, group selector or Wanted line selector and thek circuits illustrating these uses of the switch are shown in Figs. 3 Land 4.

In Fig. 3, 100, 101lv and 102 are subscribers stations. Associated with each subscribers line is ya line relay 105, an auxiliary line re-v lay 104 and a cut-off relay 103.y The yline relayk 105 and the auxiliary line relay 104 can be replaced byv a single marginal relay or by relays consisting ,of a1 semi-conductor sandwiched between two metal bodies. This yapplies also to many ofthe other rela-ys shown inFigs. 3 and 4. L in Fig. 3 is a line linder and 7S in Fig. 4 is a wanted line selector.

Switches of the general type shown in Figs.

1 and 2 can be interposed between the line finders and the wanted line selectors and arranged to act as group selectors.

rThe operation of the circuits described.

When a subscriber as 102 raises his receiver a current flows over hisr liner from the positive pole of the battery through contacts 106, 106', 1062, of the line relays of the group to which the calling subscriber belongsand then through contact 107, line relay 105, contact 108 ofthe auxiliary line relay, contact' 109 ofthe cut-off relay 103, subscribers station 102', Contact 110 of the cutoff'rielay-103, group relay 111 to the negative pole. 1

` The line relay 105 closesacircuit for itself at its'contaet-l 113 and opens its contacts 107, 106, 114 while closing its contact 1115. the closure of 115 the lwire 116: is connected to theauxiliary line relay 104. Thev starting will now be relay 111, which isconnnonfto a group of subscribers, closesits' contact 112. Thefind'er :tat-'ting current-flowsfrom the negative pole The magnet 138 thus receives an impulse and the rotor of the line iin'der is released so that the spring 23, Fig. l, drives the wipers 121, 122,- 123 round at a high speed over the bank Contact sets of theline finder. The moment the switch leaves its normal position the contacts 124, 125, 126, 119, 127 of the oitnormal switch of the line finder are closed and the Y cont-act 118 of this off-normal switch. is opened. The closure of the Contact 124 results in the energization ot the auxiliary line relay 104 by a current which flows from the positive pole through 124, 116, 115, 130, 104, 119, 102, 110, 111. The auxiliary line relay deenergizes the main line relay 105 and thereby reconnects the positive pole through 106, 106, 1062 to the other main relays as 105, 1052 so that these other relays can be ener-v gized to send further calls through the starting wire 117, 117 to other line finders. It is thus seen that when a subscriber calls he starts a certain line finder and that Vother calls made' by other subscribers each affects some. other free line finder.

' Through its contact 135 the auxiliary line relay applies'the negative ot' the battery to a contact 136 in the bank of the finder. The moment the' brush 120 reaches the contact 136 a current liovvs from the positive pole through the Contact 152. rmetallic core 9', semi-conductorsleeve 7, fixed outer metallic sleeve 19, brush 120, 136, 135 to the negative pole and the adhesion set up between the fixed outer metallic sleeve 19 and the rotary semi-conductor, sleeve 7 causes the brushes 120, 121, 122, 123 to stop on the bank contacts 136, 139, 150, 151 whereupon a current flows from the negative pole through a contact 153 of a slow-acting relay 154, Fig. 4 relay 155, contact 125, brush 123, bank contact 151, contact 156, cut-o6 relay 103 to the positive pole.v The cut-off relay 103 disconnects the calling subscribers line from the starting relay 111 and the auxiliary line rev lay 104 and the relay 155 connects the calling subscriber-s line through its contacts 157, 158 to the impulse relay 159i. The relay 155 also closesits contacts160, 161, 162 and opens the contacts' 163. 164. The closure of the con tact 161 results in the energization of the relay 165 which opens its contact 152 and closes itsl conta'c'ts'-166.A 167, 168. The relay 165 closes a locking circuit for itself which extendsfrom the positive pole through. 168, 1127 t the negative pole.

y The impulse relay 159Vv isA now energized by current fiowing through the calling subseribersf line. It closes its contacts 200, 201, 202, 203' and opens its contact 204. The closure ofthe contact 200 results in the energiiation of the' release relay 206" which closes a loch' tends threu`MY JT, 206, resistance 208 to the positive pole ot' the battery. The release relay also closes a contact 209 and thus applies the negative pole to theV core 210 ot the selector and at the same time energia-es the stepping inaenet 213 to prepare the stepln, step movements or" the brushes 214i, 215, 21T oi' the wanted line selector VIS. Ah though the ning-net 218 is energized to ree the .rotorl et the switch this switch is gior the moment liept in its normal position on account et the adhesive Jtorce set up between the semi-ceinluctor sleeve 212 and the outer metallic sleeve 211. This adhesive iorce up by a current which iows 'trom the negative pole through 269, metallic core 216, semi-conductor sleeve 212, outer metallic sleeve 211, brush 2f, wires 218, contaJt- 219 et relav 220, contact resistance 221 to the pos tive pole. lVhen the subscriber sends in his (hailingV impulses the posit-ive pole oi: the batterjv7 is alternately disconnected 'from the wire and the negative pole connected through 20D to the armature 227 is alternately disconnected from the wire 226. lVhen the positive pole is disconnected trom the wire 225 it also disconnected trom the contacts 230, and at the same time the positive pole is connected through the resistance 222 and the contact 235 to the long contacts 232, in the bank ot a wanted line selector. lillhen the positire pole removed Ytrom the long cont-act 236 the current tlowi through the metallic core 210 and througa the semi-conductor sleeve 212 and the outer nie'allic sleeve is interrupted so that the adhesive torce disappears and the spring" 23, Fig'. 1, swings the lnushes 214. 215, 6, 21? round until the brush 217 encounter the long bank contact 232 when a current will tlow troni the positive pole o1 the battery through 235, 232, 21'?, 211, 212, 216, 269 to the negative pole. lllhen the calling subscribers loop is again closed after au interruption ot the same the con tacts 202. 203 are closed and the negative pole is directly applied through 20S), 2053, 235 t so as to sliort-eircuit the current flowing` through 211, 212, 216. The adhesive torce between the semi-conductor sleeve and the outer metallic sleeve then disappears and the springv oi the selector jerlts the brushes iiorward until the wiper 21'? lands upon the long Contact 231 when a current i'iov: troni the positive pole through 219. 231. 21T` 211, 212, 210, 209 t0 the tive pole and again stop the brushes.

thus seen that the brushes 2141, 215,

1T are caused to execute two hops or vr circuit "for itself that eX- the impulse relugv 159. The banlr contacts passed over by the wipers when theyT execute two hops are arranged so as to lie in a corresponding group, say a tens group,

ot baalt contact. It will be supposed that the subscriber sends in one tens impulse so as to cause the wipers to ship round onto the long' contact 281 and that he thereupon sends in vturther impulses by which the wipers are stepped onto a particular set oi bank contacts in the tens group.

luring the pause which ensues between the tens and units dialling` impulses the change-over rela]v 240, which was previouslj,r energized by a circuit from the negative pole through 20T, 2110, 2402 to the positive pole, is deenergized and a current flows trom the negative pole through 20?, 211, oit-normal contact 212 to right hand windingl et relay 226 to the positive pole. rfhe relay 220 is thus energized and closes a locking` circuit 'for itsel't at its contact 21153 while disconneetinp,` the wires 225, 226 from the contacts 230, .,31 232, 233 and connecting the wires 225, 226 to the wires 246, 2417 which lead to bank contacts as 248, 249, 250, by means et which the selector is set onto individual benl; contact sets. At each oscillation oi the armatures of the impulse relay 159 the brush 21T will now be advanced by two'steps as `trom 25() to 251 and from 251 to 2V2in the saine manner as explained in connection with the long contacts 230, 23 232, 233.

Yilhen the wipers have thus heen set onto the bank contact set ot a wanted line another pause ensues in which the contact 255 oit' the change-over relagj7 2&0 is closed and a current then flows from the negative pole through 255, 256, test relay 25T, wiper 216, bank contact 266, cut-eti2 rela;v ot the wanted subscriberisA line to the positive pole. The test rela",Y 25? then closes its contacts 266', 261, 263, contact. 263 switching on the ringing relaiv 261. Tlhen the wanted subscriber responds a ringingv cut-oli relay 265 energized and this in turn energizes an auxiliary release rela1 266.

At the end o' the conversation the switches are restored to their normal posh tionsr b v impulses sentthrough their step pingl magnets 136 and 2123. The restoration et the line finder for example is accomplished bv sending impulses alternatel) through the stepping magnet 13S and tlnough the metallic core 9', the semi-conductor sleeve 7 and the outer metallic sleeve. rlfhe impulses sent through the core and the said sleeve perform the o'liiee of a holding pawl during` the restoration of the switch.

The negative pole is not reconneeted through Contact 1523 ot the slow relay 1541- to the relay 155 betere the latter is dcenergir-ed so that the interrupters 180, 181 will be connected through 164:, 163 and 166, 16T to the wires 182, 183.

The bearing consistingr ot the semiconductor sleeve 7 and the bracket 19 in Fig. 1 may -be modified as shown in Figs. 5 and G.

lill

lili) sleeve i In these latter gures,f19 is a bracket, `9 a metallic core, 7 a sena-conductor sleeve, 300 a split,y spring sleeve inserted between the semisconductor 7 and the bracket 19, 301` r[he bracket 19 is provided with ,an arm 305 1u whose outer end there is a hole through which kextends a threaded pin 30G that is provided with an adjusting nut and a lock nut 30S. The split'sleeve 300'is held in a rotary normal position by means of a spring 309 connected at one end to an arm 310 projecting fromv the sleeve 300 and at the other end tothe threaded pin 306. Current is conducted to the metallic core 9 by a oontactspring 311. The operation of this arresting device is as follows: Then the switch is started the core 9 and the semiconductor 7 revolve rapidly in the split spring sleeve 300 and the moment ot potentialV is applied'to the core 9 and the sleeve 300 the latter adheres to the sei'nifcouductor- 7 so that the sleeve 300 is carried around in the direction of the arrow against the action of the spring 309. The pin 320 immediately drives the detent 302 into a tooth of a toothed disk 301 so a'sto stop the wiper carrier or shaft.' The operation ot' the modified starting f circuits shown in Fig.r 13 will now be expla ined.

When a subscriber, say 400, raises f his receiver, a current Hows from the negative polethrough contact 403 of the relay 404, whiehfis common to. a group of 'subscribers, contact 405 of the line relay 406 of v'the calling subscriber, linerelay 406,

ycontacts 407, 409 of the cut-ofi' relay 408,

limb 410ot the subscribers line, subscribers station 400, second limb 411 of vthe calling line, contact 412 ofthe cut-oftrelayto the positive pole. The line relay 406 isi-nime'- diately energized and closes its contacts 413-, 414, while openingits contacts 405 and 416. By opening contact 405 and closing 413 the relay 406 changes itsL own energizing circuit so as to receive current through the relay 417 (which is common to the groupof s`ub- 'scribers) insteadof through the Contact 403.

'lhestarting relay 417 is energized and sends a starting impulse to affinder, this impulse f flowing through-403 and contact 419. yAn

energizing'current'for the relay 404 also flows `through the contact418, but betere this relay 404 is 'energized a starting current will have passed throughfthe starting wire 420. Then the 'relay y404 is energized it ydisconnects the batteryfrom the back contacts of all ot the other line relays such as 406 of the other subscribers .of fthe `group so that for the moment no other line of relay can be energized. An impulse is, however, im-

mediately sent. back from the started finder, over the wirey 421 and this impulsetlows through the contact 414, lower winding of the cutoff relay 408 to the negative pole. The cutol' relay 403 is partly energized so as to move its light armatures 422 and 427 and close the contact 423, whereby a locking circuit iior the relay 408 is established that eX- tends from the negative pole through con tact 423, contact 409, over the line of the calling subscriber and back 1 and finally through thek armature contact 412 to the positive pole.v By the operation oitI the light armature 422 the circuit of the line relayv 406`is broken at 407. lVhen the wiper of the started finder reaches the bank contact (not shown) vconnected to the wire 425 a comparatively strong current flows through this wire 425 and through 415 and the top winding ot the cut-off relay 408, causing this relay to be fully energized and to open its contacts 409, 412.

Vhen the line relay 406 is deenergized through the opening of the contact 407 the relay 417 is also deenergized to open the circuit ofA the relay 404 at contact 418. Con tact 419 of ythe relay 417 opens before contact 403 of relay 404 is closedrand a false' starting impulse is thereby prevented from flowing through the starting wire 420.

then the relays 417 and 404 are deenergizeda new starting impulse can be sent 'through'the starting wire-420 by another the call from the first flin'e being prevented from starting the second finder by its line relay vbeing rendered incapable of energizing the common relay 417 that sends starting impulses tothe finders until its cut-ofil relay is deenergized. rThis cut-off relay can, however, only be dee-ne'rgiz'ed by the `calling subscriber replacing -liis' receiver. The 'cut-off relay acts as a means for severing the normal relation between a calling line and the finder starting wire or circuitthe moment a 'finder has been started by the calling act of the calling line.- 3 f In known n'd'er starting arrangements for starting line finders one after the other, an interval of 1, 2 or more seconds generally vvelapsesy lbetween the starting of` one finder vand the next when two subscribers call at practicallyr the saine moment. more subscribers callat the same time the interval will often be -so long that the'r third subscriber' that calls will generally have com- It 4three ory inenced dialling long before a finder has conv ectcd his line to a selector. By the novel starting arrangements shown in Figs. 3 and 13 these intervals are reduced to fractions of seconds and the danger of pren'iature dialling on the part of calling subscribers is thus` practically eliminated.

llfhere lino. finders of known types that operate comparatively slowly are used, the novel finder starting arrangement will aid `Very considerably in preventing premature dialling. But where the exceedingly quickacting finders shown herein are employed a simpler finder starting arrangenient of the kind shown in Fig. 10 will generally be found to suliice. rlhis will be fully described hereinafter. i

Thetype of switch used in the system shown in F 10, 11 and 12 is illustrated in Figs. l', 8 and 0. ln 7 Li00 is a frame to which is attached a contact bank 4:01 and a re\\'i1iding magnet L102. Bent round at right angles to ine main surface of the frame, at the bottom transverse strip -103 thereof, are two lugs #l0-gl.. 40o to which is fixed by screws L106. 07 a disk lOS of agate or some other suitable Senn-conductor. Contacting with the bottom of the Semi-conductor disk e208 is a thin metal sheet 09. The disk 408 and sheet 109 are electrically insulated from the fran'ie r100 by bushings and washers of insulation surrounding the screws G, 407 in the well known manner. Contacting with the top surface of the semi-conductor disk 70S a metal disk @L10 provided with a. hemisphere Llil at the centre and a fork Li12 near its periphery. rlhe hemisphere i-11 forms the convex part of a ball socket whose concare part 13) is fixed to a shaft lli. This shaft is `iournalled in two bearings 4:15, 11o and the yielding connection formed by the ball socket 13, 411 between it and the disk ell-.0 enables all parts of the contacting surface of the latter to always keep in intimate contact with the top surface of the semi-coin ductor 08. indepemlently of any slight lateral movements that the shaft L114; may eXecutc in rotating the wipers L11T, 41S, 419, 420. rl"hese wipers are xed on a` bushing 421 and electrically insulated therefrom. Also fixed on the bushing Li21 and electrically connected with the wiper 20 is a bent arm li22 which carries the disk Ll1() around with it when the bushing 21 and the wipers are rotated by the shaft 4141. The bushing 421 is slightly longitudinally displaceable on the shaft 414, but is Vprevented from rotating relatively thereto by a. pin e223 fixed in the shaft and cngaginej with a slot 424 in the bottoni of the bushing 1121. The disk L110 is insulated from the shaft 114; by either the recessed block 1:13 or the hemisphere L111 being made oi' insulation. Slipped onto the shaftllll is a spring box 25 which is arranged to rotate relatively to the said shaft. The periphery of the spring boi; 425 is connected to the shaft L11% by a clock spring. The shaft. Llll, disk d10 and wipers 41T, 418, 11S), 120 are normally turned into an initial position in which the wiper 420 engages with a bank contact from which current tlows through the wiper L120, arm uL22, disk 110, stationary semi-conductor disk @L08 and the metal shee Li025, so as to cause the disk d10 to adhere strongly to the disk L10S and thus prevent rotation of the shaft and the wipers. lVith the shaft llll thus lixed, the spring box L125 is rotated so as to tension the spring and provide a force that tends to rotate the shaft and the wipers. rlhe spring box is held in its tensioned position by a detent 420. 1f the current fiowing through the disks 410. 408, 4.09 is now interrupted, the spring in the spring box will whirl the shaft elle and the wipers and disk-l10 round in the direction of the arrow (Fig. 8) until the wiper Lvl2() reaches a bank contact such as 42T connected to an electrical potential. The disk 110 will now again cleave to the surface of 0S and the wipers will be stopped. nubsetpiently the spring in the spring box is retensioned by means of a stepping pawl l@t28 operated by a magnet 402. ifittached to the top of the shaft is an arm 430 which is adapted to operate an off-normal contact li231 when the shaft 1iand the spring box 4125 have regained their normal positions.

ln Figs. 10, 1.1 and 12 the circuits of a line finder, group selector and connector respectively of the type shown in Figs. 7, 8 and 9 are illustrated. in these tigures 40e", S'and 60S areA the semiconductor disks similar to the disk L108 of Figs. 7 and 9. 500, Q01 and 600 are off-normal switches. l,

dell?, 41C', -120 are wipers corresponding` to wipers ell?, L11o. 119, l2() of Fig. 9. The group sel ttor, Fig. 11, has lire wipers 51T. 51o, 51S), 520, and the connector four wipers Gli', (518, 015;?. 020 that wipe over rows of bank contacts. In the group selector 511. the bank contacts 502, 503, 501, 505. 50G are group designating contacts to which potentials are alternately `applied by contacts 50T, 509 of the line relay 510.

ln the connector, 002, (30B. (S0-l, G05 are group designating contacts and between these contacts line designating' contacts such as 000, T, (509, G10. 611, 612 are placed. Potentials are applied by contacts G18, G14 of the line relay (315 first alternately to successive group designating contacts and then to suceessiye line designating contacts.

Vin the normal position the wipers of the line finder Fig. 10, are held by thc adherence of the oisk lO to the semi-conductor disk 40S, this adherence loing caused by a current that `flows from the positive pole through ott-normal contact 530, metal sheet o? .d A.08',disi: 10,4502 wiper 420', contact w relay contact ith') The wipers ofthe `group selector, Fig. 11, are heldin their normal position in a similar manner by a vcurrent that flows from the positive pole through roff normal contact 536,

rmetal sheet 537, semi-conductor disk 508,

metal disk 538, contact 539 ot relay 540, kwiper`521, bank contact 502, wire 541, contact 542 ot release relay 543 to the'negatlve pole. Similarly the kwipers of the connector are held in their normal position through a current flowing from4 the' pOSitive-` pole through off ynormal switch 630, metal sheet i 631., semi-conductor disk 608, metal disk 632',

wipcr 620, bank contactj633, wire 634, contact 635 oit releasey relay 636 to the negative pole.

The operation of the system Will appear more fully from the following description of the events which occur in setting up a connection between a calling and a Wanted subscriber. It will be assumed that the subscriber, Fig. 10, desires Aa connection with number 113. He first raises his receiver, when a current flows from the positive pole to the line lrelay 450, contact 451, line wire f 452, stationv S, line'wire 453, contact 454 of they cut-off relay to the negative pole.v 'The line relay closes lits contacts 456 and 457, the latter contact applying a negative potential to the stopping contact 458 of the line finder, ywhile the contact 456 closes an energizing circuity through the relay 459 which is the common starting relay for a group otsubscribers. lVhen the relay 459 is thus energized, a starting impulse flows trom the negative pole through 456, contact 460, armature 461, starting wiref462, oil'y normal conta-ct 463, relay 464 to the positive pole. The relay 464 isL energizedk and at its contact 535 opens the holdingy current which is normally closed through the semi-conductor 408", so that the tensioned spring of the finder whirls thc vwipers of the linder round' until the wiper: 420` reaches the stopping contact 458, when a current again flows through the semi-conductor 408 from thc negative pole rthrough line relay contact 457, stopping bank contact 458, wiper 420, disk 410` semi-conductor 408', metal sheet 531, contact 465 of the relay 466 contact 476 to the positive pole. When the wipers are thus arrested a current flows from the negative pole through the contact 467 of the ott normal switch 501, vwire 468.` relay`466,

wiper 419', contact 469, cutoff lrelay 455 to the positive pole. The cut off relay disconnects the line relay and the battery from `the subscribers line by contacts 451 and 454.v

and lowers thel potentialy on the rtest Wire 470 yby cutting in more resistance or yadditional windings of thecut off relay through opening its contact 469. The relay 466 is thus energized to close itsy contacts 471, 472, 474 and open'its contacts 465, 47 5. The positive pole, which is takenotf at contact 465, is,

however, kept connected to the metal plate 531 through the contact476 of the relay 464 which closed a locking circuit for itself through its contact 477 and contact 478 of the release relay V543.

QlVhen the release. 'relay 543 is energized` as a result ot the energization oit' the impulse relay 510 the locking circuit ot the relay 464 is opened at 478, but at the same time a positive potential applied through contact 480 and wire 481 to thc plate 531 so as to keep the holding current 'for the wipers of the finder establishedV through the semi-conductor 408/. The. release relay 543 is energized by current from the negativ-e pole through contact 479, wire 482, windings of release relay, resistance 483 to the positive pole, when the' line relay 510 is energized by cuiir'ent from the positive pole through the lett winding of the line relay 510, contact 484, trunk wire 485, 471, 417, 486, 453, calling Stanca s, 452, as?, ne', 47e, iss, 489, right hand winding ol linerelay 510 to the negative pole.

The startingwire is extended through contact 490 of the ott normal switch 500 to the next idle finder. This next finder cannot be started by current through the contact 456 of the line relay 450, because the negative pole connected through 456 to the wire 491 is `disconnected at the contact 460 when ythe armature 461 is fully pulled up so that before the otf-nr'irn'ial contact 490 is closed by the wipers ot' the finder leaving their normal position the negative pole will be, disconnected again from the wire 462. A new starting impulse cannot be sent through the wire 462 until the starting relay 459 is deenergized by the deenergization of the line relay' 450, but as the wipers of the line finder reach the bank Contact set ot" the calling linevery quickly the inter #al during which a new ot being sent is very short.

Then the calling subscriber Sis connected; through to the line relay 510 by thc lenergization of the relay 466 as described the contact509 is closed and the negative potential which is disconnected from wire 541 and the bank contact 502 of the group selector is applied through the contact 509. Then the calling subscriber, who desires connection with subscriber inthe first hundred group. sends in oney dialling impulse, i. e. causes an interruption and a subsequent closure of his line'loop to take place, the armature 492 leaves contact 509 so as to disconnect negative potential from groin) designating contact v502 and connect this potential through contact 507 to the group'designating contact 503. rfhe holding current through 508 ceases to flow tlnfough contact 502and the wipers are whirled round until the wiper 521 reaches'vvcontact 1503. Vhen the armature 492 leavesth-e contact'5`07, negative potential Ilil is removed from the Contact 508 and connected through contact 509 to the bank contact 501, so that the wiper 521 is turned orrfard until it reaches the contact 501i. 'Thus the one dialling impulse, Which resulted in the armature a02 being detracted and retracted, Caused the wiper 521 to skip first a hait step from the bank contact 502 to the contact 503 and then another'hal-.tl step trom the latter contact to the contact- 504. rlhe wipers o'l' the group selector are thus set onto the lirst group ot sets ot` bank contacts that are connected to trunks leading to the irst hundred group. During the oscillation of the armature of the line relay 510, the change-eter relay 4:93 is energized by current troni the negative pole through contact 0%. 4.03, resistance 195, to the positive pole. lhen, atter the wipers of the group selector have been set onto the desired group, the oscillations of the line relay armature cease the change-over relay 493 is short-circuited by the continued closure o't the Contact 490, so that the change-over relay L193 is deenergized to c'lose its contact L19T, whereby the relay 5&0 is energized by current trom the positive pole through 5%0, 97, oli' normal contact 4208 to the negative pole. The relay 510 closes a locking currenttor itself through its Contact Ll09 and opens contact while closing contact 550. The negative potential applied through 509, 54:1, n'iper 521, contact 539 to metal disk 538 is thus taken oilj at contact 539 and the Wipers are new whirled round until the Wiper 520 encounters the bank contact such as 551 et a tree trunk that is connected to the negative pole, when a current liows from the positive pole through lSO, metal sheet 537, semi-con ductor S, metal disk 53S, contact 550, eonta :t 552, Wiper 520. bank contact 551, Wire 5523, contact (34.0 of the release relay 636, Fig. 12 to the negative pole. The wipers et' the group .selector are thus arrested on the bank contacts 551, 556 of a free trunk and a current Itlou's 'from the positive pole through the relay 450. Wiper 519, bank contact u'ire 557, otl' normal Contact Gill to the negatiye pole. The relay 450', Whose wiper 515) brushes over its bank contacts too swiftly to permit o' its being energized by any liye contact which it passes during its hunting operation, is new energized to close its contacts 4451', ll52, 4:53, et5et and open the contacts 418i, 480 and 552. By closing the contact 451, the holding current through the Senn-conductor 508 is maintained.

lt all the trunks in the selected group are busy. the wipers of the group selector are arrested at the end et the group by means oit a special stopping contact 460 which is per inanently connected to the negative pole, and by Which holding current is sent through the wiper 520, 552, 550 and the semi-conductor 508. r)The ca'lling subscriber may be given a signal by any suitable means which apprises him o'j the fact that the trunks in the Wanted group are all busy and he thereupon replaces his receiver so as to deenergize the line relay 510 and short-circuit the release relay 543. lVhen the re'lease relay drops back, it opens at /ls'O the circuit of the relay 465, and at Llil it closes the circuit ot the stepping or'rewinding magnets 4172 and 473 et the line linder and group selector respectively. The line iinder rewinding magnet 4172 receiyes current through ell, self-interrupter Llil, 472', olil normal contact- 475, Contact 475. The spring ot the spring be): lirst Whir'ls the n'ipers of the line. linder round until the wiper titl reaches the norinal contact 532, when the olii' normal contact 530 operated by the iinder shaft is closed to establish the holding circuit through 535.

L10S. 550 to the positive pole. rthe ottnormal contact LL75 is kept closed unti'l the spring box is turned into its normal rotary position relatively to the shaft and thus current tlou's troni the negative pole through lil, -lsl reu'inding magnet all?, contact contact T5 to the positive pole until the spring in the spring box is lul'ly retensioned and the contact 155 is opened.

lVhen the release relay is deenergized as described, negative potential is applied to the contact 502 through contact 512. The metal sheet 537 is, however, kept disconnect ed from the positiye pole by the Contact 530 until this contact is closed by the shaft ot the switch rotating l'urther round until the Wiper 521 touches the Contact As the relay 5110 is also deenergized when the release relay 5-'113 drops back. a holding current Will nou flow from the positive poie through 53e, 5.27, ses, ses, e. 521. nos. on. 542 to the negative pole. The Vreu'indingl' magnet 4:73 receives current troni the negative pole through e171', 4473. selt-interruptir 4-80, oii' normal contact 481 to the positive pole, until the oil normal Contact 481 is opened by the spring box reaching its rotary normal position relatively to the lshalt ot the group selector.

Assuming that the group selettor has tounll a free trunk 553, 55T, 558, 550, cina-ent will non' ilow through the line relay (3l5 oreithecalling line, and the line relay by its contactl energizes the releafe relay (336 by current through 30. resistance (-tt to the positive pole. The release relay immediately establishes the busy condition of the seized trunk by removing negative potential from the test Wire 553 by means ot its coutact 6&0. it the same time it closes, at contactV G47, an additional path itor energizing current through the relay 1150 in the group selector'. At "'"5 the release relay (S30 dis- 00:.) connects negative potential 'from the Wire 034 and the normal bank Contact G33, so that the Wipers are advanced a short distance,

until the ywiperfiQO strikes thel bank Contact 602,` which is now connected` to the negatiye pole through 648yand l613 of thellinie ,relay 615'.' lllhen'ethe sx'ipera are moved .outofv their i'iorniai position. the oiil no'rnial ed through the oil no1-'mal cmitact.,630y to thevinetal `sheet 631, anda stopping4 cir# cuit 4for the Wipers 'is' thus clo'sedmthr'o'ugh the semi-,conductor 608'The stepping niagnet or rewinding magnet 650 is:- energiz'edy i through contact 651 ofthe rele'zserel'aly and through the rsecond oil-.norjn'ial contact '6,52

kwhichT is controlled `by the' springv box' of; the selector.` The stepping niagnetor rewinding magnet 650 continues receiving current r'oni the negative pole through Contact G551/.foil

normal contact` 652,' 650, sel'finterrupter'653 to fthe positiye,pole,` until ,the spring boX regainsits rotarynormalposition 'relatively to' the shaft ofvthis connector,`- vTheContact 652 is then. opened tofedeenergize the Ina'gg net 650. Thedcen'ergizatioirof the "release relayv 636 also results in the opening,`at conf,

tact 647., of the circuit ot the relay the group selector, Fig. 11,l so thatrel'a'y 510 is deenergizecl by theopeningfoff Contact 484 and the group selectorrelease relay 543 is 'short-circuitedY and j applies `negative, potential through its Contact 542to1 the `bank contact 502 While disconnecting positivefpr'otentia'l rat contact 480 vfromthe bottom plate 537.4 The springk of the group selector now Whirls lthebrushes round untilthey reach their normal position'in which the brush 521 touches contact 502 and positive potential is reconnected',through the oii'norrna'l conf tact 536 to .the bottom plate v537. vThe i brushes are then heldagainst yiurtherr roplatre 531endsimultaneously the lopeinaj Qf release ref.

tary' movement. The stepping magnet 473',l Whose circuit closed at471fy Whenthe re'-` l'ease relay is deenergized, rewindsthe spring box and when this bo'X 1has regained its nornial position relative to the brushv shaft the second off-normal switch ,opens the rewind!` ing magnet circuit atMcontact 481". y, Y, yThe deenergization,v of release relay`I` also causesthe restoration'of the line Fig. 10, for when"theContact 48OIis openedy noe'iti've potential` is oil'Y the. bottoni the yrelay free is de'energized by l lay 'contacte/470C 4The s 'ring (if: the fiadeif 110W' ivhirlsl round( .the

nder amer-e i unk a 'current ilo s tact 530,v platef531, semi-conductor 408, brush 420", bank contact 532, contact 535 to theknegative pole.v The finder rewinding' inagnet 472 is energized when ther release relay 542 is deeuergizedand it steps the spring box round until its circuit (negative pole 471', 474, 472, 475,475', positive pole)` .is opened by .the secondl oil-normal switch 475er the finder.

Assuming that the callingsubscriber pro-L -fg-eeds `with vthe call, hie will send in a tens dialling inipulse and thus cause the arinature to execute one oscillation, whereby the negative potential is reinoved from the groi'ip designating bank contact 602 and placed on `the group designating contact 603 throughthe back Contact 614 and back'contact 654 of` relay 655, and thenrernoved again from 603 and reconnected to the group designating Contact 604.v This causes the Wiper 620 to bernoved first fronrthe bank Contact 602l to 603 and then froin 603 to 604, i. e-` up to the desired group in 'the contactbankl r .i e When the line relay 615 oscillates its armature in responseto the` tens dialling impulses, thel change-over relay 660 is energized Vby current from the negative pole through645', 660, 662 to the positive pele, but When the tensdialling iinpulses cease the change-.over relay 660 is short-circuited by the Contact 664 of the line relay/so that theccontact 665 isrclosed to'establi'sh a circuit from the `negativepolethrough 665, oil normal contact 666.righthand Winding of relay 655; This relaycloses its contacts 667, 666, 669, 670 andopens contactsw648 and 654. At Contact 668 the relay 655 closes a locking circuit iorritsell". and at Contact 667 rit prepares circuit for the busy tone relay 672. By opening contacts 648, the relay 655 disconnects the contacts 613, 614 from the group designating bank Contact oi the con.- nector and connectsthein through 669, 670 to the line designating bank contacts oi? the saine. When the contact '648 is, opened and the contact 670v closed, the negatiye potential applied through 6133is transferred from the group designating contact 604 to the line designating contact 673 and therefore the wiper 620 is nioved to the Y contact 673. When the calling' subscriber' now sendsin two, units dialling impulses the negative potential kis"disconnected ironi contact 673fand applied to contact 674 andthen reconnccted to 675 during theiirst impulse, and then disconnected froni the Contact 675, connected to th bank contact 676 andA reappjlied to bank. c'ontact`w677, during thev secondunits dialling iinl'gu'lsfe; 'Thevwiper`620 isthuslniovedv roni contct'gto Contact until it reaches the con ti'fct'677. ;Di'irir"ig the sendingin'of the units Y f dialling inipulsesthe change-over relay660f i; i y .contacts 67's; 6 faf'whue closing its: Contact 68o; By

lua)

the latter contact it establishes an energizing circuit through 680, 667, relay 672 to the positive pole. This relay closes a locking circuit for itself at its Contact 681 and prepares a path for the busy tone from the busy tone device 683. lllhen the units impulses have all been sent in and the wipers of the connector have been set onto the set ot' bank contacts belonging to the wanted line, the change-over relay 060 is again short-circuited so that the contacts 678 and 079 are closed. Negative battery eonnected through 07S to the test relay 080 and it the wanted line is tree the test relay will be energized to immediately open the contact GST and close its contacts GSS, 689, 090 and 091. It the wanted line is busy the contact 6ST will remain closed and a busy tone will be applied from 683 through (ST9, 682, 6ST, G92 to the calling line. The calling subscriber will then hang up his receiver and the switches will he restored in the manner already described.

Assuming that the wanted line is 'free and that the test relay G80 ha's been energized, the ringing relay 69T will be intermittently energized by current impulses from the positive pole through 098, 69T, 691, 699 to the negative pole. rllhe ringing generator 700 will thus send out ringing current impulses through contacts 701, T02. lVhen the wantod subscriber responds the ringing cut ott` relay 703 is energized and the ringingl current is cut oli by the contact G99 beingopened. The ringing' cut oit relay closes a locking circuit tor itselt by its contact 705.

The connector may be arranged to be restored to normal in any desired manner when the wanted subscriber hangs up.

In Figs. 7 and 9 a tlexible connection between the wiper shaft and the contacting metal disk 110 is shown in the :torni ot' a ball socket 4:11 and a carrier 422 whichcarries the disk 410 around with it. A modified form ot flexible connection is shown in Fig. 17. ln this modified llexible mechanical connection the end ot the shaft is tapered and rests in a Haring or conical cavity t300 in the disk S10. Carriers in the lorm ot arms 822 are provided which are ineclianimilly lixed, but electrically insulated from. the sha lt S14. The ends S15 of these carriers are forked and studs 810 fixed in the disk 010 extend between the prongs ot the forks and transmit the rotary motion of the carrier 822 to the disk 810.

The semi-conductor 408 in Figs. i' and 9 is fixed to the trame L100. It may. however, in some cases prove to be advantageous to provide automatically operating means for cleaning the top surface of the semi-conductor from time to time. Such automatic means are illustrated in Figs. la to 1f. In these Figs. 108 is the semi-conductor, 410 the contacting metal disk, 412 the/carrier for carrying round the metal disk, and 113 the ball socket between the wiper shaftft and the metal disk. The semi-conductor is mounted upon a bracket 900 which extends from a sleeve journalled on a vertical post 902. Attached to the sleeve 901l is a ilexible disk 903 provided with a peripheral iron ring 904. Rotating near the metal ring 901 is an iron disk 905 which is arrai'iged lo he magnetized hy a coil 900. lVhen the revolving disk L)05 is ,magnetized the ring 901 is attracted so that it. rotated to swing the sleeve 901 with the bracket 900 and the semiconductor e108 mounted thereon round the pillar 902. rl"he sleeve 901 carries a bent arm 910, at whose top end there is mounted a roller 911 of insulation. This roller. when the sleeve 901 is rotated in the direction oi the arrow, bears against the lower surface ot' a Contact spring 912 so that this spring is forced into contact with an upper spring 913. The springs 912 and 913 keep an en ergizing circuit ot the coil 900 closed while the bracket 900 is swung round in the direction ot the arrow. This circuit beingl initially closed by a contact of the switch at the moment it is released or restored to its normal position. lVhen the roller 911 reaches the end ot the inclined contact spring 912 this latter moves down away from spring 913. The energizing circuit through the coil 901 is thus opened and the driving disk 905 deenergized. A helical spring- 911 now swings the bracket 900 back into its normal position shown in Fig. 111-. During this restoring movement ot the bracket 900 the roller 911 rides over the top surface ot the spring 912 so as to prevent the energizing circuit of the coil 906 from being closed again. During these swinging moveinentfi of the bracket 900 with the semi-conductor disk 1108 the latter moves past a brush 920 which cleans the top surface of the semiconductor. The brush 920. which is shown in Fig. 1+i in broken lines. is held by a bracket 921 attached to the pillar 902. The lower portion oiY the bracket 921 to which the brush 920 is attached is broken away in Fig. V1.-.L so as to more clearly show the bent arm 910. The brush 920 is lined between a bar 922, Fig. lt. and a. strip 92B by means ot' screws 921. The brush 920 may consist ot tufts ot' hair or ot a strip ot rubber.

Then the bracket 900 is swung away from the metal disk 110' the latter is held suspended by loops or staples which embrace the ends of the carriers 412.

lVhen the bracket 900 with the semi-con ductor 408 is swung away from the disk 410 it is at iirst moved slightly downward so that, during the rest of its swinging movement, thetop surface of the semi-conductor 1108k is at a lower level than the bottom surface of a metal disk L110. The said slight downward movement may be brought Til about 'thepart of the ring 904 that registers with the disk 905 when the ring 904 is in its normal positionwith a hump 930 so that the sleevek 901, in addition to being rotated by the disk 905, willy also be pulled slightly downward. The downward movement may Valso be effected by a pin 931 projectii'ig from the pillar 902 into aslot 932 inthe sleeve 901, which latter slopes downward at its one end as shownin Fig. '14.

The current sent through the' semi-conductor may be supplied from-mains or a battery of higher ypotential than the current source used for the electromagnets and electromagnetic relays. The said battery of higher potential may be a battery of dry cells, because the current required for the semi-conductor circuit is very small.- y

Under certain conditions the idea underlying the present invention, viz. to obtain an extraordinarily sudden effect that ywill very abruptly stop travelling contacts on any desired relatively fixed Contact, maybe realized to a certain extent by employing an electromagnet whose armature is continually in direct contact with its pole, but which is only caused to adhere to the pole at proper moments by sending a current through its windings.

I claim:

l. A switch con'iprising bank contacts, brushes adapted to glide in a continuous .motion over any desired number of said bank contacts, a continually acting power device tending to move said brushes, an arresting means bot-h for holding the brushes in an initial position against the actiony of said power and for positively stopping vthe y'power-driven brushes on any desired ba-nk contact,

Q. A switch comprising bank contacts, brushes adapted to glide in a continuous motion over any desired number of said bank contacts, a continually acting power device tending to more said brushes, an arresting means for holding the brushes in an initial position against the action of said power device and` for rst positively stopping the power-driven brushes at a plurality of points arranged at certain distances apart and for then positively stopping the brushes after they have travelled a shorter distance than the distance between two said points.

A switch comprising bank contacts, brushes adapted to glide in a continuous motion over any desired number of said bank contacts, a continually acting power device tending to move said brushes, an arresting means for holding the brushes in an initial position against the action of said power device and for first positively stop- 4ping the power driven brushes at a plurality of points arranged at certain distances apart and for then positively stopping the brushes at a yplurality of other points placed closer together than the saidiirst points.`

1i. A switch comprising bank contacts, rotary 'brushes adapted to glide in a continuous motion over any desired number of said bank contacts, a continually acting power device tending to move said brushes, an' arresting means for holding the brushes in an initial position against the action of said power device, for positively stopping the power-driven brushes on any desired bank contact and for finally stopping the brushes again in their initial position.

5. In a switch, bank contacts, a wiper co operating with the bank contacts, a wiper carrier, a metal surface moving together with the wiper carrier, a semi-conductor bearing against the said metal surface, and an electric ycircuit for affecting the adhesion between the said metal surface and semiconductor, thesaid circuit including the said surface and semi-conductor.

6. Inr a switch, bank contacts, a wiper cooperating with the bank contacts, a wiper carrier, a metal surface moving together with the wiper carrier, a continuously acting power device for driving the said carrier, a semi-conductor bearing against the said metal surface, and an electric circuit for affecting the adhesion between the said metal surface and semi-conductor. y

7. In an automatic telephone switch, bank contacts, a set of wipers cooperating with the bank contacts, a wiper carrier, a metal surface moving together with the wiper carrier, a semi-conductor bearing against the said metal surface, and an electric circuit for affecting the adhesion between the said metal surface and semi-conductor, the said circuit including rthe said surface, semiconductor, wiper and a said bank contact.

8. A switch comprising bank contacts, rotarybrushes adapted to glide in a continuous motion over any desired number of said bank contacts, a continually acting power device tending to move said brushes,

an arresting` means for holding the brushes in an initial position against the action of said power device and for first positively stopping the power-driven brushes at a plurality of points arranged at certain distances apart and for then positively stopping the brushes after they have travelled a shorter distance than the distance bet-Ween two said points and for subsequently stopping the brushes again in their initial position.

9. A switch comprising bank contacts, rotary brushes adapted to glide in a continu- 'ous motion over any desired number of said bank contacts, a continually acting power device tending to move said brushes, an arresting means for holding the brushes in an initial position againstthe action of said power device and for firstpositively stop- CSi isc

ping the power-driven brushes at a plurality ot points arranged at certain distances apart and Ytor then positively stopping the brushes :it a plurality 0l other points placed closer together than the said first points and for subsequently stopping the brushes again in their initial posit-ion.

l0. A switch comprising bank contacts, a brush carrier With brushes adapted to glide in continuous motion over any desired nuniber of said bank contacts, a continually acting'poiver device tending' to nieve said brush carrier, two conducting` parts in Contact with each other one of which is a senil-conductor, and one of which is fixed to the brush carrier While the other is held stationary, electric circuits cti-operating with said conducting parts; said circuits and conducting parts formingan arresting means `for holdingthe brushes in an initial position against the action ot' said power device and for positively stopping' the power-driven brushes on any desired bank Contact.

In testimony whereof I have signed this specification.

FRITZ ALDEDORFF 

